An Immovable Object Meets an Unstoppable Force
by LittleDarling13
Summary: During an outing, Saitama and Genos meet another hero, Grey Granite, and learn something new about Mumen Rider. Oneshot. MumenRiderxOC, Mumen x OC, Just a sweet little story for someone who doesn't get enough love.


Forgive me if this sucks, this is my first time writing fanfic in 3+ years. This story will be based off of the anime. It is in the point of view of Saitama and Genos, and it takes place a few days after the defeat of the Sea King.

Disclaimer: I do not own One Punch Man, Mumen Rider or any other affiliated characters.

They were in G-City to get a bargain on cleaning supplies, as Genos had used the last of the glass cleaner two days ago and their broom had gotten broken during a monster attack prior that week. Unfortunately, it seemed like their shopping would have to wait.

A Tiger level threat had been announced. A large creature had been spotted, half-man and half-fire hydrant, calling itself 'The Red Spout.' All businesses had been shutdown due to possible flooding and civilians have been encouraged to stay in their homes. So, Saitama and Genos ran in the direction of pillars of water, planning to assist the heroes that had been called hopefully before the time the store normally closed in the evening. Where the monster was rampaging in a water-logged plaza, two B-Class heroes were attempting to take down the menace. On the other side of the plaza, a group of refugees were hiding behind a stone statue. Saitama had Genos assist with defeating the monster while his interest was peaked by the strange statue.

The statue was of a woman in a defensive pose; her forearms crossed in front of her face, her body in a position ready for impact and a fierce look in her eyes. Saitama thought it might be a statue in memory of a fallen heroine, but there was no plaque or pedestal. The statue was obviously of a hero though, or maybe a dominatrix now that he saw the outfit she wore. It was a tight catsuit, with wedge heeled combat boots and a matching utility belt. Suddenly, the civilians behind the statue began to cheer.

After carefully analyzing his foe, Genos attacked with a great blast. As the steam cleared, the outline of the monster could be seen in the smoke.

"Fire? FIRE?! You think that fire can defeat me! I am the-one-who-controls-water, he-who-needs-no-hose, the great Red Spout!"

Instead, Genos leapt into the air and smacked the fire-hydrant man right on the dome of his head. Like an over-pressured water tank, the monster cracked and exploded with great force, knocking back the two B-Class heroes who grumbled about an S-Class taking their fight. The two men washed up by the solid statue and Genos landed beside his sensei. A voice came from behind them, "Ah, Demon Cyborg. Thank you for completing my mission while I was unable to lead my team."

A woman stood with a soft smile on her face. The two heroes were outraged that she was giving their credit to the S-Class hero, "But Grey Granite! After your heroic sacrifice and our defense of the civilians afterward, we should be getting the credit!"

"Yeah! Why give the credit to the S-Class and his sidekick?"

Saitama, in his normal oblivious confusion, obstinately asked, "Who is this woman?"

The B-Class heroes were shocked beyond belief, "Who is she? Why you phony! This is Grey Granite, A-Class Hero Rank 23. She has the power to turn her body into solid rock, with a finishing move of turning to immovable granite! The ultimate A-Class defender! Not only that but she is also Akiyama Seiko, public idol and two-time Olympic Champion. She is a million times better than you'll ever be Caped Baldy, the C-Class nobody!"

"Now Tanktop Black Hole, if Caped Baldy and Demon Cyborg hadn't arrived, you and Crying Man would have been defeated. Just because I turn to stone doesn't mean I can't hear what is happening around me. And for the record, I never actually turn to granite." The exasperation on her face was apparent. "It is called wurtzite boron nitride, a very hard mineral that when its bonds flip I become unmovable and much harder than diamond. Granite is a relatively weaker substance. I still think it's unfair that the public picks our names if we don't come up with something when we register." Now Grey Granite was really pouting.

"Eh? Why weren't you helping with the fight if you're a hero?" Saitama was still not getting the picture.

"Sensi, this woman, the A-Class hero Grey Granite, whom has the power to turn her entire body to stone including her hair and clothes, cannot move for some time after she has used her ability. To become unmovable, her body becomes solid rock the entire way through and the bonds of the mineral change. As I am sure you know, sensei, it takes time for these bonds to change back to their original form. Based upon my analysis of the battle she had been frozen for 8 minutes before we arrived on the scene, and you yourself went to check on her, Saitama-sensei."

"Ah" Saitama was already bored of the cyborgs long-winded explanation and was walking away. "Come along, Genos, the market is back this way."

"Wait, Caped Baldy-shi. May I accompany you for a moment?" Grey Granite suddenly seemed quite serious. "I can walk with you toward the grocery store, I just would like a minute of your time."

"You should not have to ask for his time! He should be groveling for yours! The useless phony should be apologizing for interrupting your -" Tank Top Black Hole was once again shot down by the heroine. "You are dismissed. If you continue with this behavior I will put in a request with the Association to never work with you again. Maybe that will teach you to be respectful." Genos also was glaring at the B-Class, his piercing gold gaze showing his displeasure. Then he turned to see if his teacher would accept Seiko's request.

Saitama gave a short nod. "Fine, but don't walk too slow. We are already later than planned because of this detour." Grey Granite gave him a heart-stopping smile. Or what would have been a heart-stopping smile if Saitama still had access to his emotions.

"So… Did you have something to say, Akiyama-san?" They had been walking for a little over two minutes and Seiko had yet to say anything. "Well, Caped Baldy-shi, I just wanted to -" " _"Please_ just call me Saitama." "Then I ask that you call me Seiko, Saitama-sama. As I was saying, I wanted to thank you for your work in J-City. I came very close to losing Daisuke that day."

As she continued thanking Saitama, Genos was analyzing her. _This hero, Grey Granite, speaks very respectfully to Sensi. She has obviously heard the rumors but since she is still so kind meaning that she either does not believe them or has seen the true strength that Sensi possesses. She most likely heard it from this person Sensi saved. But all of the civilians heard what Sensi said in defense of the other heroes, putting himself down and being a credit-stealer. So "Daisuke" must be a hero. But she is also thanking Sensi specifically. This leads to only one conclusion._

"How did you meet Mumen Rider-san?"

Both Saitama and Seiko looked owlishly at Genos' sudden comment.

"Eh? This is about Mumen Rider?" Saitama, ever the epidemy of social unawareness, was again confused.

"Yes, Sensi, Seiko-san is thanking you for saving Mumen Rider-san. Daisuke must be his real name. I have come to the conclusion after analyzing how Seiko-san is speaking with you. She has obviously heard of your strength and believes in it, but has never seen you fight. Someone told her, most likely Daisuke who was at the shelter during the Sea Folk invasion. But you told the civilians that you only finished the monster off, so he isn't one of them. And you weren't there when the Sea King mauled the other heroes. But you did however step in to save Mumen Rider-san. Which leaves one logical conclusion, that Daisuke is Mumen Rider's civilian name. What is not logical is how a mid-level C-Class Hero is known quite well by an A-Class Heroine. So brings about my previous question, 'How did you meet Mumen Rider-san?"

Saitama only turned to look at Seiko.

She shrugged and rubbed the back of her neck. "Well, its kind a long story, but Daisuke and I are dating."

Saitama was actually surprised. He looked at the woman beside him, then imagined the couple together side by side. It really didn't add up. Seiko is a tall, shapely woman with steel-blue hair falling in gentle waves, tan skin with very professional make-up. Mumen Rider is more like him, down to earth and quite common in the long run.

But then again, who was he to judge or question them?

"We met after a mission I completed in M-City. I was still a statue after the battle, my teammates at the time, Sneck and Mountain Ape, had already left since they finished off the Mysterious Being. Daisuke had been helping by getting civilians out of harms way and directing emergency services to those who were trapped or injured. He noticed I was still a statute and stayed by me until after my transformation had worn off. Had a bottle of water and a towel ready for me. It was really sweet. No one had ever thought to take care of me like that. Other heroes normally treat me like Tank Top Black Hole, like I am a princess who should be treated as such, or they think I am a uptight snob like Sweet Mask since we are both considered idols. Daisuke doesn't care about any of that, he just wants the best for everyone. I was so worried when I heard he had been in J-City… Even after only 11 months of dating I don't know what I would do if I lost him."

Genos fixed her with his solemn stare. "J-City was in great peril, Mumen Rider's courage was the only thing to save those people and myself from total annihilation. If he hadn't kept getting back up, the Sea King could have killed everyone in the shelter before Sensi got to the location. I have not given it much thought until now, but I will write a letter to the Association detailing his efforts requesting him to be advanced in rank."

"While I am sure he would appreciate your actions, Genos-san, Daisuke's heart is with the people. He would just as well be content with you expressing your gratitude the next time you meet." Suddenly, Seiko's phone buzzed. "Ah, it seems the Hero Association would like a report of the battle with the Mysterious Being and then I have an interview with WKCM. It was a pleasure to meet you both, and thank you again Saitama-sama for all of your work. Maybe I can put in a word about changing your hero name, but we will have to think of something clever… Ah anyway, I am sure I will see you both around!" With a tilt of her head and a smile, the heroine turned the other way and began walking the other direction.

"Hey Genos?"

"Yes Sensi."

"Something has been bothering me. That other guy said she was an Olympic Champion."

"Yes Sensi."

"What sport did she compete in?"

"Akiyama Seiko won a silver and a gold in the last Summer Olympics, three years ago. She competed in the Women's Road Race and Individual Time Trials. These are cycling events."

"Well that explains a lot."

Well that's the end, please give some constructive feedback.

In the anime, Mumen Rider's real name isn't revealed so I picked Daisuke because it means "great help" and that seemed fitting. Seiko means "force" and Akiyama means "mountain" which I thought was pretty clever on my part. I love having names with hidden meaning.

If enough people like this, then I'll try to turn it into a full story of how Seiko and Daisuke meet and fall in love and all that fun stuff. Might do some more one-shots too so look out for those!


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